It has heretofore been common to electrically stimulate nerve fibers for various therapeutic purposes, and medical practitioners have heretofore used electrical signals for various other purposes, including, for example, stimulation of muscle activity and producing of various sensations.
The sequence of effects produced by electrical stimulation, as its intensity is increased, is known to generally follow a pattern of a perception of electrical sensation (usually tingling), an increase in sensation, fasciculation muscle contraction, pain, and then more severe demonstrative effects such as electrical burns or cardiac arrhythmias.
While therapeutic effects often occur while stimulation is applied with a continuous intensity below that necessary to produce muscle contraction, exceptions do occur in the general effect pattern such as, for example, when a steady DC current is applied in slowly increased intensity, muscle contraction cannot be obtained, though the sequence of effects occur in the same order, and, for example, in a DC overdose situation, electrical burns can occur.
Electrical stimulation has been attempted and/or realized through use of a wide variety of electrical waveforms and these waveforms have ranged from purely DC (galvanic) current or voltage to many different combinations of electrical pulses of various shapes and durations. While at least some such waveforms have provided some degree of desirable effect, the results achieved have been random with no clear understanding of how such waveforms might be combined and/or grouped to enhance results.
As mentioned above, stimulation has been made to occur with many different types of pulses, and use of pulse pairs that include both positive and negative pulses have heretofore been suggested (see, for example, U.S. Pat. Nos. 2,375,575, 3,946,745, 4,237,899, and 4,256,116).
While these patents suggest that biphased pulsed pairs can be utilized for therapeutic purposes, there is no apparent teaching in these patents of combining different types of biphased pulses to achieve dual ends.
Apparatus and method directed to optimizing stimulation using biphasic pulses is shown and claimed in U.S. Pat. No. 4,640,286, entitled "OPTIMIZED NERVE FIBER STIMULATION" issued Feb. 3, 1987 to Thomas H. Thomson, and in U.S. Pat. No. 4,803,988, entitled "NERVE FIBER STIMULATION USING PLURAL EQUALLY ACTIVE ELECTRODES" issued Feb. 14, 1989 to Thomas H. Thomson, both of which patents are assigned by the assignee of this invention. Nerve fiber stimulation using biphasic pulses in a symmetrical pattern is shown and claimed in U.S. Pat. Application Ser. No. 07/009,760, issued Mar. 26, 1989 as U.S. Pat. No. 4,813,418, which application is the parent application of this application as stated above.
It has also been heretofore suggested that edema can be reduced and wound healing can be enhanced by application of negative DC to a wound. Application of negative pulses to a wound (as well as application of positive pulses and combinations of alternately positive and negative waveforms) to effect wound healing is shown in U.S. Pat. Application Ser. No. 07/103,696 filed Oct. 2, 1987 by Katherine H. Miller, entitled "SOFT TISSUE WOUND HEALING THERAPY UTILIZING PULSED ELECTRICAL STIMULATION", issued July 11, 1989 as U.S. Pat. No. ,846,181, and assigned to the assignee of this invention.